METHOD OF SURGICAL CORRECTION OF PRESBIOPIA IN COMBINATION WITH MYOPIC ASTIGMATISM

摘要

FIELD: medicine.;SUBSTANCE: invention relates to field of medicine, namely to ophthalmosurgery. Cornea is influenced by layer-by-layer ablation with pulse irradiation of non-scanning excimer laser with Gauss radial distribution of energy density in transversal section of ray and formation of concave relative to anterior cornea surface surfaces. Exposure is carried out by successive reduction of parametre of mean-square deviation of energy density distribution in each of following pulse series within the interval from 2.3 mm to 1.6 mm. Value of energy density amplitude in centre of pulse symmetry, which is within the interval from 175 mJ/sq.cm to 100 mJ/sq.cm is also successively reduced with each following pulse series. Within each pulse series values of parametres of mean-square deviation of energy density distribution and energy density amplitude are constant. Each pulse series forms concave relative to initial cornea surface spherical surfaces, located on one axis, and zone of exposure is symmetrical relative to optic centre of cornea symmetry. Primarily first concave spherical surface is formed, ratio of diametre of first concave spherical surface to cornea diametre being within the interval from 0.6 to 0.8. Further, second concave spherical surface is formed, ratio of diametre of second spherical surface to diametre of optic zone being in interval from 1.0 to 1.1. After that third concave spherical surface is formed, ratio of diametre of third spherical surface to diametre of optic zone being in interval from 0.28 to 0.55. Cornea surface is exposed to irradiation of excimer laser with wavelength 193-250 nm, diametre of laser impact zone is from 5 to 9 mm, pulse duration 15-30 ns, pulse recurrence rate from 5 to 15 Hz.;EFFECT: method allows to minimise volume of removed tissues, reduce probability of post-operation complications, increase number of optic surfaces.;2 tbl, 3 dwg, 2 ex